The antibacterial
activity of essential oils extracted from medicinal plants (Ocimum gratissimum,
L., Cybopogum citratus (DC) Stapf., and Salvia officinalis, L.)
was assessed on bacterial strains derived from 100 urine samples. Samples were
taken from subjects diagnosed with urinary tract infection living in the community.
Microorganisms were plated on Müller Hinton agar. Plant extracts were applied
using a Steers replicator and petri dishes were incubated at 37°C for 24
hours. Salvia officinalis, L. showed enhanced inhibitory activity compared to
the other two herbs, with 100% efficiency against Klebsiella and Enterobacter
species, 96% against Escherichia coli, 83% against Proteus mirabilis,
and 75% against Morganella morganii.

Historical records indicate that, as long as 2,600 years ago, the Chinese already
developed drugs using a number of forms of phytotherapeutic agent elaboration.
This was also the case with the Egyptians, Greeks and Romans.

In light of the recent emergence of bacteria which are resistant to multiple
antimicrobial drugs, posing a challenge for the treatment of infections, the
need to discover new antimicrobial substances for use in combating such microorganisms
becomes patent.

The Brazilian savannah is very diverse and rich. It includes a number of plants
that are used in natural medicine for treating tropical diseases, including
bacterial infections.1,4 On the other hand, due to the lack of knowledge
concerning the potential toxic activity and adequate usage, medicinal herbs
are often used incorrectly, thereby not yielding the desired effect.

Cymbopogom citratus (DC) Stapf. essential oil is includes mircene, neral,
geranial, and other unidentified compounds2 and is used for fighting
colds, dysentery, headaches, and also as a tranquilizer and antispasmodic, besides
its antimicrobial activity.8

Ocimum gratissimum L. is widespread in the tropics. It is used in popular
medicine for treating upper respiratory tract infections, pneumonia, cough,
fever, and conjunctivitis. The oil extracted from this plant contains the following
compounds: 1,8 cineol, eugenol, methyl-eugenol, thymol, p-cimene, cis-ocimene,
and cis-caryophyllene, and, in different concentrations inhibited the growth
of Staphylococcus aureus, Shigella flexneri, Salmonella enteritidis,
Escherichia coli, Klebsiella sp., Proteus mirabilis, and
Pseudomonas aeruginosa.6

The essential oil extracted from S. officinalis, L., used as a medicinal
herb, has antibacterial activity due to the presence of 1,8-cineol3
and of an antifungal substance.5

One hundred samples were collected from the middle portion of the urine of
patients diagnosed with urinary tract infection in the municipality of Caçapava,
southeastern Brazil. The samples collected were striated on DIFCO agar petri
dishes and incubated at 37ºC for 24h. The colonies isolated were identified
by biochemical testing. The three herbs were picked between 10 a.m. and 3 p.m.
from the Agrarian Science Department of the Universidade de Taubaté,
state of São Paulo.

Essential oil extraction was performed using the hydrodistillation technique
proposed by Craveiro et al2 (1981). 100 g of leaves (herb) and 250
ml of water were placed in a 500 ml Kitassato. Upon heating on a Bunsen burner,
a stream of vapor was generated and was collected using a 75 cm serpentine.
The oil was then separated from the water with the aid of a 500 ml separation
funnel.

One hundred ml of each strain were plated on Müller Hinton agar. The oils
extracted were applied using a Steers replicator and petri dishes were
incubated at 37º C for 24h. Reading was done by observing microbial growth
inhibition at the sites where essential oils were applied.

Of the 100 samples analyzed, 79% were of Escherichia coli. Other enterobacteria
were observed at levels below 8%. Pseudomonas aeruginosa accounted for
1% of samples.

The antimicrobial
activity of the essential oil extracted from Salvia officinalis L. showed
a mean 79% de inhibition (Table 1).

A comparison of the activity levels of the three herbs showed the greater efficiency
of Salvia officinalis L. The different species analyzed were over 96%
effective against Escherichia coli, 100% against Klebsiella pneumoniae,
over 83% against Proteus mirabilis, 75% against Morganella morganii,
100% against Enterobacter aerogenes, and 100% against Klebsiella oxytoca.
There was no antimicrobial activity on Pseudomonas aeruginosa.

Although less efficient than Salvia officinalis L., O. gratissimum
L. and C. citratus (DC) Stapf. Showed antimicrobial activity on 16% of
the strains analyzed, with the exception of Klebsiella oxytoca and Pseudomonas
aeruginosa.

Escherichia coli was the most frequent etiological agent of urinary
infection among the subjects analyzed.

The bactericidal activity of the medicinal herbs studied was satisfactory,
especially that of Salvia officinalis L. An adequate toxicological study
must be carried out so as to verify the possibility of using these herbs for
fighting microorganisms.

A single
strain of Pseudomonas aeruginosa was resistant to the three oils analyzed.
This species is of great importance in hospital infections, and it deserved
a wider ranging investigation, including a larger number of strains.